1. Field of the Invention
The present invention relates to various kinds of keyboard instruments, including electronic keyboard instruments such as an electronic organ, an electronic piano, and so on.
2. Description of the Related Art
Electronic keyboard instruments such as an electronic organ, an electronic piano, and so on generally have a keyboard including many keys being performance operating elements at upper portion of an instrument main body and speakers at under portion of the same, so that a musical sound signal at a pitch selected by key operation of the keyboard is generated by a built-in electronic circuit and transduced into acoustic sound by the speakers, thereby emitting a musical sound.
For example, in an electronic keyboard instrument described in JP 2002-244661A, a pair of right and left speaker boxes are provided under a key bed for holding the keyboard of the instrument main body.
Further, there is another instrument as found in JP 2002-297141A, in which a part of the speakers being a sound generator (a speaker for high tones) is located at upper portion of a case of the instrument main body, and a tone emitting portion for the tone generated by the speaker is formed between a top panel and a keyboard cover thereunder.
In any of such conventional electronic keyboard instruments, however, acoustic waves mainly directly emitted from the speaker being a sound generator to the front side (performer side) are heard by the performer and audience. Further, as found also in the aforementioned patent documents, a music stand board and a keyboard cover opened are generally erected at upper portion of the instrument main body, which are provided on the front side of the tone emitting portion, and therefore may interfere with tone emission from the tone emitting portion and cannot even in the least provide echo effect.
There is another instrument in which the speaker is located such that its vibration surface horizontally lies at a rear of the keyboard to make a thin instrument main body. This arrangement, however, brings about a problem of difficulty in the performer hearing tones from the speaker.
Hence, to solve the problem, the speaker is located at the rear of the keyboard and inclined to face the performer as in the instrument disclosed, for example, in JP 2720459B. However, a sufficient volume of the speaker box cannot be ensured, failing to make sound quality better especially within a low range.
As described above, acoustic waves emitted from the tone emitting portion of the sound generator such as a speaker or the like are not sufficiently effectively used in the conventional electronic keyboard instrument, leaving room for improvement in entertaining the performer and audience with a sufficiently rich and powerful performance tone.
Further, the instrument main body (case) of the keyboard instrument is generally constituted of a holding portion for holding a keyboard, side panels on both sides thereof, a back panel on the rear side, a key slip on the front side, and an upper surface cover member covering the upper portion on the rear side of the keyboard. To secure the rear portion and the front portion of the upper surface cover member to the back panel and the side panels, screwing is required at many points. In addition, the screwing is performed using attachments on the lower surface side to hide the screws from view form outside, and thus the attachment work consumes considerable effort and cost.
There is still another instrument in which the upper surface cover member is composed of a fixed portion fixed to the top portion of the instrument main body and an opening/closing cover portion for opening/closing the keyboard, and opening/closing of the opening/closing cover portion is damped by a damper mechanism attached to the instrument main body. In the instrument, however, since a strong reaction force acts when the opening/closing cover portion is closed using the damper mechanism, the fixed portion on the front side may be lifted up and peel off from the instrument main body.